How do I efficiently create a TRIGGER which, on occasion, generates a VIEW? - sql

Question

On a small pre-registration database, I'm using the following SQL to generate a VIEW whenever a specific user name is given. I'm using this mainly to get a snapshot whenever a sysadmin suspects duplicate names are registering. This will be done rarely (atmost once per hour), so the database schema shouldn't be getting excessively big.
CREATE OR REPLACE TRIGGER upd_on_su_entry
AFTER UPDATE OR INSERT
ON PRE_REG_MEMBER
FOR EACH ROW
BEGIN
IF :new.MEMBER_NAME = 'SysAdmin Dup Tester' THEN
EXECUTE IMMEDIATE 'CREATE OR REPLACE VIEW mem_n AS SELECT :old.MEMBER_NAME, COUNT(:old.MEMBER_NAME) FROM MEMBER GROUP BY MEMBER_NAME';
END IF;
END;
However, this appears to be a bloated, inefficient and erroneous way of working (according to my admin). Is there a fundamental error here ? Can I take an equivalent snapshot some other way?
I'm very new to SQL, so please bear with me.
Also, I want to be using the view as :
public void dups()throws Exception
{
Calendar cal = Calendar.getInstance();
jt.setText("Duplicate List at : "+ cal.getTime());
try{
rs=stat.executeQuery("select * from upd_on_su_entry");
while(rs.next())
{
jt.append(rs.getString("MEMBER_NAME")+"\t");
jt.append(rs.getString(2)+"\t");
}
}
catch(Exception e){System.out.print("\n"+e);}
}

Answer 1

There seem to be some misunderstandings here.
1.) views are basically stored sql statements, not stored sql results, so your view will always display the data as it is at the point of querying the view.
2.) Never ever use DDL (create statements) and similar during normal processing of an application. Its just not the way databases are intended to work.
If you want a snapshot at a point in time, create a secondary table which contains all the columns of the original table plus a snapshot time stamp.
When ever you want to make a snapshot copy all the data you want from the original table into the snapshot table while adding the current time stamp.

Answer 2

Based on your comment, it sounds like you want something like this
SELECT MEMBER_NAME FROM PRE_REG_MEMBER
GROUP BY MEMBER_NAME HAVING COUNT(*) > 1;
This will return all members with more than one row in the table

Answer 3

Again, ask yourself "what am I trying to do"?
Don't focus on the technology. Do that after you have a clear idea of what your goal is.
If you are just trying to avoid duplicate registrations on your database, just search the users table and show an error if that username is already there.
Also, think of your datamodel carefully before going into the implementation details.